Superfrequency oscillatory means



Feb. 10, 1942. H; w. KOHLER 2,272,211

I SUPERFREQUENCY OSCILLATORY MEANS Filed March 16, 1940 2 Shegts-Sheet 1 III VENTOR Hans W hohler v ATTMHEY Patented Feb. 10, 1942 SUPEBFR-EQUENCY OSCILLATOR]? MEANS Hans W. Kohler, Washington, D. 0.

Application March 16, 1940, Serial No. 324,240

(Granted under the act of March 3, 1883, as amended April 30, 1928; 374) O- G- 757) 14 Claims.

This invention relates to ultra-high frequency oscillatory apparatus and particularly to vacuum tubes capable of generating extremely short waves at high power levels.

Among the several objects of this invention are:

To provide electronic discharge means wherein the impedances of the connections to the electrodes are extremely small and the associated tank circuits are impedance matched to the inter-electrode impedances;

To provide simple and eflicient means for generating ultra-high frequencies at high power levels;

To provide a capacitively loaded coaxial line of reduced physical length wherein electronic discharge electrode elements are directly carried by parts of the coaxial line.

The manner in which the above and other objects are attained will be made clear by a perusal of the following description in connection with the accompanying drawings, wherein: Fig. 1 shows diagrammatically a coaxial line short circuited at both ends with the inner conductor open intermediate its ends;

Fig. 2 illustrates a coaxial line generally corresponding to that in Fig. l but with the inner conductor portions capacitively loaded and a vacuum tub connected thereto as part of an oscillatory circuit;

Fig. 3 illustrates a circuit equivalent to that Fig. 2 but with the reactive constants lumped;

Fig. at shows a push-pull oscillatory circuit utilizing the principle disclosed in Fig. i;

Fig. 5 is a longitudinal section of a coaxial line having a triode electron discharge device built directly therein;

Fig. 6 illustrates the principle of my invention embodied in an oscillatory system of the tuned plate-tuned grid type;

' Fig. 7 is in general like Fig. 6 but the electron discharge device is a pentode instead of a triode as in Fig. 6.

it is known that the input and output impedances of vacuum tubes used in ultra-high frequency, or super-frequency, work are relatively small, due to electron transit time effects and hence the impedances of tank circuits as seen from the tubes must likewise be relatively small in order to match properly the tube impedances. Also, the effect of the load on these impedances must be given due consideration.

Furthermore, the parameters of the tank circuits must be such that they, and not the interelectrode capacitances of the tube, essentially delength, although resonant to the same frequency termine the resonant frequency. The present invention provides means for efiectively fulfilling these requirements. The underlying principle of my invention is developed from the very elemental disclosure in Fig. 1 to the final, and at present preferred; embodiments in Figs. 5 to 7.

Fig. 1 depicts a coaxial line short circuited at both ends, wherein the numeral 8 designates the outer conductor or shell having a length equal to one-half wave length of the desired frequency. The inner conductor is open intermediate its ends and consists of the portions 9 and ID. This line has two fundamental modes of vibration, (l) with the two halves in phase'or (2) with the two halves in phase opposition, as indicated by the dotted lines It in Fig. 1 showing the instantaneous voltage relations. It is with the second mode of oscillation that this invention is concerned.

Fig. 2 discloses the device of Fig. 1 developed a step further.

Here the outer conductor 8 has a physical length much less than one-half wave as in Fig. l, which is brought about by the capacitive loading of the inner conductors 9' and with inter-leaved, capacitively cooperating elements I: and 03 carried by the inner conductors 9' and M respectively. The oscillatory system is completed by the electron discharge tube lit whereof the anode is coupled through blocking condenser M5 to capacitive elements l3 and the grid ll is connected to capacitive elements i2. Cathode it of tube It is coupled to outer conductor 3 through by-pass condenser l9 and is grounded at 20. Grid leak Eiconnects shell 3 to ground and furnishes the bias potential for grid ll, thus putting shell 8 at D. 0. grid potential. The plate supply is through shunt feed choke 22. The inner conductors El and it are of unequal length in order that the anode-cathode and grid-cathode impedances of the tube may be matched by the impedances in the external circuit.

Fig. 3 is a diagrammatic representation of a' Hartley oscillator circuit having lumped con stants and equivalent to the apparatus in Fig. 2. The several elements in Fig. 3 corresponding to the parts oi Fig. 2 have been designated by the same reference characters, except that the resonant circuit in Fig. 3 which is the equivalent of the coaxial line in Fig. 2 has been designated by the numeral 89.

Fig. shows diagrammatically how the structure in Fig. 2 may be modified to produce a push,

pull oscillator. The intemal conductors 3 and I. or the coaxial line are of equal length, for purposes of symmetry, and respectively carry the cooperating capacitive elements I! and I3. Anode 23 of tube 24 is connected to inner conductor 3 and anode 25 of tube 26 is connected to inner conductor I.) at a point thereon that is substantially the same distance from the 'capacitive means carried thereby as is the connection of anode 23 to inner conductor 9. Likewise the grids 21 and 23 are symmetrically connected to the inner conductor other than that to which the plate in the same tube is connected. The cathodes 23 and 3! are by-passed to outer conductor 3 by capacitances 3i and 32 and both cathodes are grounded, the circuit being completed through grid leak II.

The devices above set forth may be utilized substantially in the manner shown. Oscillators as shown in Fig. 2 have been tested and have opcrated satisfactorily in the frequency range from 43 megacycles to 400 megacycles. By varying the loading capacitance of the inner conductors a frequency range in the ratio of 3%:1 has been covered with a single tank or coaxial line. The arrangement in Fig. 4 provides increased power output. When a single tank is used for both plate and grid circuits, neutralization is not possible but if separate tanks are used for these two circuits neutralization in the conventional manner may be eflected.

The power output may be increased still further by incorporating the electron discharge electrode elements directly in the tank circuit of Fig. 2, as shown in Fig. 5. Here the outer conductor 33 has a conductive closure 34 at one end and conductively mounted thereon in coaxial relation with shell 33 is an inner conductor 35 carrying capacitive elements 33. Disposed within shell 33 in coaxial relation therewith is a conductive member 31 carrying a second inner conductor 33 provided with capacitive elements 38 inter-leaved with capacitive elements 36. The member 31 is insulatingly supported within shell 33 by means oi insulating studs 40 engaging a supporting disk 4i and the base 03 of member 31.

A cathode 43, shown as being of the unipotentinl type, is supported by a disk ll secured to base 32 but conductively separated therefrom by insulation ll whereby the cathode 43 is capacitively by-passed to the base 42 thereby putting the cathode substantially on radio frequency ground potential. The cathode supply is by means of leads 1'' and grid connection is through lead G. The grid 43, which may be of the squirrel cage type open at one end, is connected at its open end to the inner conductor 33 to surround the cathode l3 and the anode I! in turn surrounds the grid 33 but is mounted on inner conductor 33.

The output is taken of! by means of the hairpin inductive coupling 33 extending within the member 31. The spacing between members 33 and 31 constitutes a blocking condenser by the grid 43 and the direct current potential applied to anode 41 through lead 43. A trimmer condenser may be connected to the leads II. The spacewlthin shell 33 is made hermetically tight by a glass closure 3| secured to shell 33 by a glass-to-metal seal and is evacuated to the desired degree. The leads F and G are brought out through a press I! in closure I I Fig. 6 differs from Fig. 5 in that it provides an oscillatory device of the tuned plate-tuned grid type. Shell 33 has conducting ends 34 and and an inwardly extending partition or septum 58. It is to be understood that the end members 54 and 55 are originally separate from ell l3, otherwise assembly of the device would be impossible. They are shown as being integral however, since they may be welded or sweated or otherwise secured to shell 53 to form a substantially integral structure. septum 56 carries on one face a set of capacitive elements 51 and on its other face a set of capacitive elements 58 that respectively cooperate capacitively with the elements 59 and" carried by inner conductors ti and 62.

The inner conductor 6! is carried by end member 33 while inner conductor 52 fixed to a cupshaped portion 83 insulated from end 54 by annulus El and insulatingly supported in shell 53 by air-gap E5, the spacing between member 63 and end portion 54 and the portion of 53 forming airgap 65 with 63 constituting a blocking condenser between the plate supply 49 to anode 51 and grid 36 conductively mounted on inner conductor' 8|. The current supply to filament BI is through two concentric tubes 69 and 10 that are insulated from each other and constitute a bypass condenser between the terminals of the file.- ment. The tube 69 is conductively connected to a cup-shaped member H which constitutes a bypass condenser between the grid and the filament. The grid and filament leads are brought out through a glass shell 12 and the space within shell 53 is evacuated.

It will be observed that the shell 53, the member 83 capacitively coupled thereto and the inner conductor 82 with its capacitive loading 60 constitute a tank circuit for anode 51 while the shell 53, end 55 and inner conductor 61 likewise constitute a tank for grid 66, the two tanks being separated by the eil'ect of septum 56. It will be observed that there is zero length of lead between the anode 51 and its tank circuit and the grid 68 and its tank circuit. Owing to the blocking between the grid circuit and the anode circuit, the coupling is through the inter-electrode capacitances only.

The device shown in Fig. 7 is like that illustrated in Fig. 6 except that the screen grid 13 and suppressor grid 13 are added to constitute a pentode electron discharge device. The screen grid 13 and suppressor grid H are respectively connected to by-pass condensers II and 16 which are assembled in position with the integral por tion 11 and thereafter the members 18 and 13 are placed thereagainst and secured as by means of welding 33.

It will of course be understood that the webs II between the capacitive elements, and the capacitive elements themselves, may be slotted to reduce eddy current losses. Likewise, it will be seen by those skilled in this art that the capacitive elements carried by the inner conductors may be made relatively movable with respect to each other to permit of changing the value of the loading capacitance, such adjustment of the capacitive elements being effected through a magnetic clutch, a bellows or other well known means.

I am aware of previous structures of a nature somewhat similar to my present invention, such as that shown in the patent to Dallenbach. 2,128,233. However, my invention differs therefrom in that it provides capacitive loading in excess of that due to the interelectrode capacity, in that it is adaptable for separately tuned input and output circuits and in that the outer conthe capacitive loading means may be disposed radially inwardly of the tube electrode elements.

The invention herein described and claimed may be used and/or manufactured by or for the Government of the United States of America, for

' governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. An oscillatory system, comprising a vacuum tube having a cathode, a grid and an anode; an elongated conductive shell having a conductive closure at each end, a respective conductive linear member coaxially secured at one end to each said closure in conductive relation therewith, one of said members being longer than the other, loading capacitive means including two sets of meeting elements, each said set being respectively conductively connected to the other end of one of said linear members, whereby to constitute a coaxial resonant line, means connecting to said grid the shorter linear member, means coupling said anode to the said elements connected to the longer linear member, means capacitively coupling said cathode to said shell, means connecting said cathode to ground and a resistance connecting said shell to ground, the electrical length of said shell and capacitively loaded linear members being substantially one-half wave length of the desired frequency while the physical length thereof is muchless.

2. An oscillatory system, comprising an elongated conductive shell having a conductive closure at each end, a respective conductive linear member coaxially secured at one end to each said closure in conductive relation therewith, a -respective capacitive loading means connected to each said linear member and in cooperative relation with each other, whereby to constitute a coaxial resonant line; two vacuum tubes each having a cathode, a grid and an anode; means coupling each said anode to a respective linear member at a point spaced from said capacitive means, means connecting each said grid to that linear member to which the anode of the other tube is coupled, the point of each said grid connectlon being more remote from said capacitive means than the said point of coupling of the anode of the other tube, means capacitively coupling each said cathode to said shell, means connectlng each said cathode to ground, and a resistance connecting said shell to ground.

3. .An oscillatory system, comprising an elongated conductive shell, a respective conductive linear member conductively connected at one end to a respective end of said shell, respective capacitive means connected to the other end of each said linear member and in cooperative relation with each other, whereby to constitute a coaxial resonant line; a vacuum tube having a cathode, a gridand an anode; means connecting said grid to one said linear member, means coupling said anode to the other said linear memher, the impedance of said resonant line at the point of connection of said grid and the point of coupling of said anode being matched to the tube impedance respectively in circuit at such points, means coupling said cathode to said shell, means connecting said cathode to ground, and a resistance connecting said shell to ground.

4. An oscillatory system, comprising an eiongated conductive shell, a respective conductive linear member conductively connected at one end to a respective end of said shell, respective capacitive means connected to the other end of each said linear member and in cooperative relation with each other, whereby to constitute a coaxial resonant line; two vacuum tubes each having a cathode, a grid and an anode; means coupling each said anode to a respective said linear mem ber, means connecting each said grid to the linear member to which the anode of the other tube is coupled, the point of connection of each said grid to the respective linear member being more remote from said capacitive means than the point to which the anode of the other tube is coupled, means coupling each said cathode to said shell, means connecting each said cathode to ground, and a resistance connecting said shell to ground.

5. An oscillatory system, comprising a coaxial resonant line having an external member and an internal member in two parts, a set of capacitive elements carried by each said internal mem-- her part, said sets being in cocperativecapacitive relation; a vacuum tube having a cathode, a grid and an anode; means placing one said part operatively in circuit with said grid, means placing the other said part operatively in circuit with said'anode, the impedance of each said part being matched to the tube impedance with which such part is in circuit, means'coupling said cathode to said external member, means connecting said cathode to ground, and a resistance connecting said external member to ground.

6. An oscillatory system, comprising a coaxial resonant line having an external member and an internal member in two parts, a set of capaci tive elements carried by each said internal member part, said sets being in interleaved capacitive relation; a vacuum tube having a cathode, a grid and an anode; means placing one said part oper atively in circuit with said grid, means placing the other said part operativcly in circuit with said anode, the impedance of each said part be-- ing matched to the tube impedance with which such part is in circuit, means coupling said cathode to said external member, means connecting said cathode to ground, and means to apply an operating bias to said grid. a

'7, Ultra-high frequency means, comprising an external conductive shell, the space within said shell being evacuated, an internal conductive member in two parts mounted ccaxially in said shell, at least one of said internal member parts being conductively connected to said shell, respective capacitive means carried by each of said internal member parts, said capacitive means being in interleaved capacitive relation with each other, and means cooperating with all the aforesaid members and means, togenerate ultra-high irequency oscillations.

- 8. An ultra-high irequency device, comprising a first circuit section and a second circuit section; said first, section comprising an elongated conductive shell, a shorter conductive portion coaxially mounted therein in conductive relation therewith at one end, a plurality of spaced capes itive elements conductively mounted on the other end 0! said shorter portion, a grid mounted within said capacitive elements and conductively connected to said shorter portion, an electron emissive cathode mounted within said grid and insulated therefrom; said second section including an elongated conductive outer shell disposed about said fir a conductive sure for one end of said outer shell, an inn onductive member conductively mounted on closure to be coaxial with said outer shell and with said shorter portion, an anode member conductively mounted on said inner member disposed around said grid, a plurality of capacitive elements conductively mounted on said inner member in operative capacitive relation with the capacitive elements on said shorter portion; means insulatingly supporting said first section within said outer shell, output coupling means insulatingly sealed in said closure extending within the shell of said first section, a closure for the other end of said outer shell, and two conductive leads to said cathode and a conductive lead to said grid, all said leads being sealed in said closure for said other end of the outer shell in insulated relation, the space within said outer shell being evacuated.

9. An ultra-high frequency device, comprising a first circuit section and a second circuit section; said first section including a conductive shell, a conductive linear member disposed coaxially therein and conductively connected thereto at one end, a grid conductively mounted on said linear member at the other end thereof, an electron emissive cathode mounted adjacent said grid but insulated therefrom, a plurality of spaced capacitive elements conductively mounted on said member adjacent said grid; said second section including an outer conductive shell disposed coaxlally about the shell in said first section, a conductive closure for one end of said outer shell, a conductive inner member mounted on said closure coaxially with said outer shell, an anode member conductlvely mounted on said inner member adjacent said grid, a plurality of capacitive elements conductivelymounted on said inner member in operative capacitive relation with the first-mentioned capacitive elements,

a closure for the other end of said outer shell,

and respective supply means connected to said anode, said cathode and said grid, the space within said outershell being evacuated.

10. An ultra-high frequency device, comprising a first coaxial resonant tank portion including an outer shell, a closure for each end of said shell, an inner member of less length than said shell coaxial with said shell and conductlvely connected to said shell; a second resonant tank portion including a second shell within said outer shell and coaxial therewith, a linear member coaxlally mounted in said second shell and conductively connected thereto; loading capacitive means having two sets of elements whereof one set is conductively mounted on said linear member and the other set is conductively mounted on said inner member, means insulatlngly supporting said second resonant tank in said outer shell, an anode mounted on said inner member, a grid mounted on said linear member adjacent said anode, and an electron emlsslve cathode mounted adjacent said grid but insulated therefrom, the space within said outer shell being evacuated.

11. An ultra-high frequency device, comprising a coaxial line having inner and outer members short circuited at both ends, said inner conductor being open intermediate its ends, capacitive loading means interposed in said inner conductor where said inner conductor is open, an anode connected to said inner conductor at one side of the point where said inner conductor is open, a

ection shell coaxially therewith,

grid connected to the inner conductor at the 1'8 other side of said point and positioned to cooperateowith said anode, an emissive cathode positioned to cooperate with said grid and said anode to form a triode, the impedances of said triode being matched to the impedances of said coaxial line at the points where said cathode, grid and anode are respectively connected.

12. An ultra-high frequency oscillatory device disposed adjacent said grid and capacitively coupled to radio frequency ground; a second inner conductor coaxial with said shell, means capacltively coupling one end of said second inner mem-- ber to the other end of said shell, members coaxial with said shell carried by said second inner conductor to cooperate capacitively with the flanges on the other said face of said septum, an anode carried by said second inner conductor adjacent the grid on the side of said grid opposite said cathode, the space within said shell being evacuated; said first inner conductor, the said members carried thereby and said shell having an impedance matched to the impedance between said grid and said cathode and constituting a resonant tank for said grid; and said second inner conductor, said members carried thereby and the said means capacitively coupling said second inner conductor to said shell, and said shell, having an impedance matched to the impedance between said anode and said cathode and constituting a resonant tank for said anode.

13. An ultra-high frequency oscillatory device of the tuned plate-tuned grid type, comprising an elongated conductive shell closed at both ends and having an inwardly extending septum provided on each face with a plurality of spaced flanges coaxial with said shell; a first inner con ductor coaxial with said shell and conductlvely connected at one of its ends to one end of said shell, members coaxial with said shell carried by said first inner conductor disposed to cooperate capacitively with the flanges on the face of said septum adjacent thereto, a grid conductively connected to said first inner conductor, a cathode disposed adjacent said grid and capacitively coupled to radio frequency ground; a second inner conductor coaxial with said shell, means capacitively coupling one end of said second inner member to the other end of said shell, members coaxial with said shell carried by said second inner conductor to cooperate capacitively with the flanges on the other said face of said septum, an anode carried by said second inner conductor adjacent the grid on the side of said grid opposite said cathode, the space within said shell being evacuated; said first inner conductor, the said members carried thereby and said shell having an impedance matched to the impedance between said grid and said cathode and constituting a resonant tank for said grid; two spaced capacitive means disposed in said septum, a respective grid connected to each said capacitive means and disposed between the first-mentioned grid and said anode; and said second inner conextemel conductive anci We ewpemtfing eweci w v tively leaded fimemai cemduetors, and electronic discharge eiecerede elements operetively associated with eeid internal centimeters whereby said ez'ztemeicenducwr and me sf said internal conducwre constitute an anode tank cireuit and said eztemei conduct/er end the other said imemel eemiueter censtitum a grid ten]; circuit, sew eiremts'hemg so related their, the respective volttherein are in whese epimsition.

' HANS W. KOHLER. 

